312 THE HOUSE FLY— DISEASE CARRIER 



Inasmuch as chemical disinfection can be reHed upon 

 to destroy pathogenic bacteria, and inasmuch as burial 

 greatly reduces the danger from animal parasites, a 

 suitable combination of the two methods (chemical dis- 

 infection and burial) can be used with reasonable safety. 



(5) Sewers: In partly sewered towns, the effluent 

 from these privies may be emptied into the sewers. If 

 conditions are such that the addition of this material 

 to the sew^age is dangerous, then the entire sewerage 

 system needs correction. 



Paper. — Only toilet paper so far has been used, and 

 the septic action seems to digest it. Other experiments 

 indicate that newspaper would be disposed of by septic 

 action in the tank, but perhaps some increase in the 

 size of the tank would be required. 



Cleaning. — Although no water has been added since 

 the model was put into operation, the contents of the 

 liquefying tank have remained fluid, and it is prob- 

 able that in a tank having the capacity of an oil bar- 

 rel, the amount of sludge from the dejecta of a family 

 of five people would not be sufficient to require the 

 cleaning of the liquefying tank oftener than once in 

 six months to a year. 



